Ok , 1988 s23, 5.7. Is settingthe timing as simple as hooking up my timing light to #1 ignition wire and setting the base timing to 8 degrees? I checked it shortly after I bought the boat and it was set like at 12 or so BTDC.... please advise on proper method to adjust timing..
You just need to be sure the timing advance is in whatever state Mercruiser wants it in for the timing to be checked. More than likely, that just means at an idle, but you should check the manual (or perhaps someone lurking knows).
at idle, marine engines use flyweights to advance timing inside of the distributor so you want to make sure the timing isn't advancing, simply on the older stuff check at idle, keep your light on the marks and raise the rpms to insure the timing advances with rpm and you will see this at the marks, distributors have been known to rust up and and break the flyweight springs and so on, so always take a look under the roter for broken springs and rust...thats what advances the timing for the engine unlike a car which uses vacuum advance timing
New twin 4.3's - 235hp each with Alpha 1 Gen 2 Drives
Re: Ignition timing
Depending on which Thunderbolt ignition you have, you may need to ground the timing wire. I have the Thunderbolt V and it's a purple/white wire. When you ground this it prevents the electronics from trying to adjust the timing at the same time you're making the base adjustments. What I've always done is ground it with the engine off and remove the ground with the engine off so you don't damage anything.